1. Field of the Invention
This invention relates to an ambulation control apparatus and an ambulation control method to be used for a robot having a structure adapted to behave like a living body with an enhanced level of reality. More particularly, the present invention relates to an ambulation control apparatus and an ambulation control method to be used for a bipedal ambulatory robot having a structure that mimics the bodily mechanism and the motion of an erect bipedal animal such as man or ape.
To be more accurate, the present invention relates to an ambulation control apparatus and an ambulation control method to be used for a bipedal ambulatory robot adapted to erect bipedalism and having the upper half of the body including the torso, the head and the arms mounted on the lower limbs. More particularly, it relates to an ambulation control apparatus and an ambulation control method to be used for a robot that mimics the motion of man including gestures with startling reality and walks on its two legs without losing balance.
2. Description of Related Art
A robot refers to a mechanical apparatus that moves like man, utilizing electric and/or magnetic effects. The word xe2x80x9crobotxe2x80x9d is believed to be originating from a Slavic word xe2x80x9cROBOTA (slave machine)xe2x80x9d. Robots became popular in Japan in the late nineteen sixties but many of them were industrial robots designed for the purpose of automation and manpower-saving in factories including manipulators and carrier robots.
As a result of massive research and development efforts in recent years in the field of bipedal ambulatory robots having a structure that resembles the bodily mechanism and the motion of an erect bipedal animal such as man or ape, robots are expected than ever to find practical applications. The bipedal ambulatory robot adapted to erect bipedalism has an advantage that it can softly walk, getting over an obstacle and stepping up and down a staircase without difficulty.
It should be noted here, however, that the research and development of bipedal ambulatory robot historically started from studies on various aspects of motion of lower limbs and was not directed to entire erect bipeds.
For instance, Japanese Patent Application Laid-Open No. 3-184782 discloses a joint applicable to a structure corresponding to from-the-torso-down of a bipedal ambulatory robot.
Japanese Patent Application Laid-Open No. 5-305579 discloses an ambulation control apparatus of a bipedal ambulatory robot. An ambulation control apparatus according to the above patent document is adapted to control a bipedal ambulatory robot in such a way that the ZMP (zero moment point) of the robot on the floor where the robot is walking agrees with a target position. The zero moment point is a point on the floor where the moment of the robot due to the reaction of the floor is equal to nil. However, it is clear from FIG. 1 of the above patent document that the torso 24 that gives rise to the moment is a sort of black box and the document proposes only lower limbs of a bipedal ambulatory robot and not an entire robot that mimics man.
However, to many researchers, obviously the ultimate object of research and development of bipedal ambulatory robots is realization of a structure that looks like and moves like man. To be more accurate, a bipedal ambulatory robot is a structure adapted to erect bipedalism and having lower limbs good for walking on its two feet, an upper half of the body including a torso, a head and arms (hereinafter to be referred to simply as upper limbs) and a trunk section linking the upper limbs and the lower limbs. A complete robot should be so controlled that it stands upright and walks and works on its two feet, moving the upper limbs, the lower limbs and the trunk section in a coordinated manner according to a predetermined priority scheme.
A bipedal ambulatory robot that simulates man in terms of motion and bodily structure is referred to as humanoid robot. A humanoid robot can support our daily lives in various scenes of living.
Bipedal ambulatory robots can be roughly categorized into those to be used for industry and those to be used for entertainment.
Robots for industrial applications are mostly designed to replace men m various different industrial scenes and do difficult works for men in the field of manufacturing, construction, power generation and so on. For example, robots of this category replace men in atomic power plants, thermal power plants, petrochemical plants and other plants for maintenance works and in manufacturing factories and sky-scraping buildings for various dangerous and difficult works. Thus, robots of this category are so designed and manufactured as to operate for a specific application or function in a specific way, although they walk on two feet. In other words, they are not required to have a structure that mimics the bodily mechanism and the motion of an erect bipedal animal such as man or ape. For instance, while they may show high degrees of freedom at a specific part of the body in order to work for a specific application by moving in a delicate way, the degrees of freedom of other parts of the body that are not directly related to the application such as head and waist may be left low. As a result, inevitably, such robots may move awkwardly and may not appear particularly agreeable.
On the other hand, robots for entertainment are more closely related to our daily lives rather than adapted to carry out difficult works and supporting our lives. In other words, robots of this category are designed to copy the physical mechanism of erect bipedalism of men and apes and move smoothly. As they are a sort of copies of erect mammals such as men and apes who are highly intelligent, they are preferably rich in expressions. In this sense, they are exactly humanoid robots.
In short, while robots for entertainment share the essential technologies with those for industrial applications, they are totally different from each other in terms of hardware mechanism, method of controlling motions and software configuration for achieving the ultimate object.
As well known, the human body has joints whose number exceeds several hundreds and hence shows several hundred degrees of freedom. While a robot preferably shows the same degrees of freedom if it mimics perfectly the behaviour of man, to achieve such high degrees of freedom is technologically highly difficult because a single degree of freedom requires the use of an actuator but a robot provided with hundreds of actuators is totally impractical in terms of manufacturing cost, weight and size. Additionally, a robot with high degrees of freedom requires a volume of computation that increases exponentially for controlling the position, action and balance.
To summarize, a humanoid robot has to be designed to emulate the bodily mechanism of man with limited degrees of freedom. Additionally, a robot for entertainment is required to behave like man and be rich in expressions with degrees of freedom far lower than the human body.
Additionally, while a bipedal ambulatory robot adapted to erect bipedalism can softly walk, getting over an obstacle and stepping up and down a staircase without difficulty, the operation of controlling its attitude and walk is difficult because its center of gravity is rather high. Particularly, a robot for entertainment should be so controlled for its attitude and stable walk that it remains rich in expressions.
Meanwhile, the xe2x80x9cexpressionxe2x80x9d of man or ape heavily relies on the motion of the upper limbs including the arms and the torso in terms of not only carrying out a work but also manifesting its feeling. Such a motion is referred to as xe2x80x9cgesturexe2x80x9d.
In our daily lives, gestures appear almost constantly on our bodies while we are standing or walking or otherwise moving on our feet. Additionally, the center of gravity the entire body of a person moves significantly to give rise to the moment of inertia while he or she is gesturing. Men and apes are so created that they can keep on standing or walking by autonomously compensating the balance of the center of gravity and the moment of inertia.
On the other hand, a humanoid robot is required to be rich in expressions as pointed out above and hence gestures are indispensable to it. Therefore, the robot needs attitude control and stable walk control in response to a gesture for which the upper half of the body takes a major role.
A number of techniques have been proposed for controlling a bipedal ambulatory robot in terms of attitude and stable walk. However, most of the known techniques are those adapted to make the ZMP (zero moment point) of the robot where the moment of the robot due to the reaction of the floor is equal to nil agrees with a target position.
For example, Japanese Patent Application Laid-Open No. 5-305579 discloses a bipedal ambulatory robot that is controlled in such a way that the ZMP of the robot on the floor where the robot is walking agrees with a target position.
Additionally, the bipedal ambulatory robot of Japanese Patent Application Laid-Open No. 5-305581 is so configured that the ZMP is located in the inside of the supporting polyhedron or at a position separated from the ends of the supporting polyhedron of the robot by a predetermined margin when one of the feet of the robot touches down on or lifts off from the floor. With this arrangement, the robot can maintain its stability of walking if subjected to external disturbances because of its safety margin of a predetermined distance.
Japanese Patent Application Laid-Open No. 5-305583 also discloses a technique of controlling the walking speed of the bipedal ambulatory robot by way of ZMP target position. More specifically, the bipedal ambulatory robot of the above patent document uses preselected walk pattern data and the leg joints of the robot are so driven as to make the ZMP agree with a target position, while the inclination of the upper half of the body is detected, so that the rate of delivering the preselected walk pattern data is modified according to the detected value of inclination. As a result, if the robot rides on unexpected undulations of the floor and becomes forwardly inclined, the rate of delivering the preselected walk pattern data is raised to allow the robot to restore the proper attitude. Additionally, since the ZMP is so controlled as to agree with a target position, there arises no problem if the rate of delivering the preselected walk pattern data is modified when the robot is standing on its two feet.
Still additionally, the Japanese Patent Application Laid-Open No. 5-305585 discloses a technique of controlling the touch down position of either of the two feet of the bipedal ambulatory robot according to the target position of the ZMP. More specifically, the bipedal ambulatory robot of the above patent document either detects the discrepancy between the target position and the actually detected position of the ZMP and drives one or both of the legs to eliminate the discrepancy or detects the moment around the ZMP target position and drives the legs so as to make the detected moment equal to zero.
Furthermore, the Japanese Patent Application Laid-Open No. 5-305586describes a technique of controlling the inclined attitude of the bipedal ambulatory robot by way of the ZMP target position. More specifically, the bipedal ambulatory robot of the above patent document detects the moment around the ZMP target position and, if any moment is detected, it drives the legs so as to make the detected moment equal to zero for stable walk.
Besides, known documents including xe2x80x9cThe Data Book of Bipedal Ambulatory Robotsxe2x80x9d, (2nd edition), A General Study (A) Subsidized by the Ministry of Education, xe2x80x9cA Study on Ambulation and Control of a Bipedal Ambulatory Robotxe2x80x9d, Research Group (February, 1986) and xe2x80x9cThe Development of a Bipedal Ambulatory Robot Adapted to Compensate the Tri-Axial Moment by a Motion of the Upper Limbsxe2x80x9d (6th Symposium on Intelligent Moving Robots, May 21 and 22, 1992) describe bipedal ambulatory robots comprising at least upper limb joints for driving the upper limbs and a plurality of leg joints linked to the upper limbs and adapted to drive the leg joints for walking, wherein the gait of the upper limbs is determined on the basis of that of the lower limbs (and hence any instability of the attitude of the robot due to the motion of the legs is corrected by the gait of the upper limbs).
Thus, the above pointed out known techniques are not adapted to control the attitude and the stability of walking of the robot by taking motions where the upper limbs of the robot takes a major role into consideration. In other words, the above techniques are for recovering the stability of walking of a bipedal ambulatory robot by modifying the attitude of its upper limbs (and their motion that changes with time) when the robot can no longer keep on walking due to external disturbance. Differently stated, those techniques are intended to modify the attitude of the upper limbs of a robot where the lower limbs takes a major role in walking in order to correct their instability due to external disturbances so that the techniques neglect the expression of the upper limbs. Additionally, the techniques described in the above documents cannot recover the stability of attitude if it is lost in the course of a gesture for which the upper limbs take a major role.
In view of the above pointed out technological problems, it is therefore an object of the present invention to provide an ambulation control apparatus and an ambulation control method for effectively controlling a robot having a structure that is adapted to mimic the mechanism and the behaviour of a living body.
Another object of the present invention is to provide an ambulation control apparatus and an ambulation control method for effectively controlling a bipedal ambulatory robot having a structure that is adapted to mimic the mechanism and the behaviour of an erect biped such as man or ape.
Still another object of the present invention is to provide an ambulation control apparatus and an ambulation control method for effectively controlling an erect bipedal ambulatory robot having lower limbs adapted to erect bipedalism and amounted with an upper body half including a torso, a head and arms.
Still another object of the present invention is to provide an ambulation control apparatus and an ambulation control method for effectively controlling a robot so as to make it walk stably and keep on behaving like a man and being rich in expressions.
A further object of the present invention is to provide an ambulation control apparatus and an ambulation control method for effectively controlling an erect bipedal ambulatory robot having lower limbs adapted to erect bipedalism and amounted with an upper body half including a torso, a head and arms so as to make it recover the stability of attitude whenever the latter is lost due to an action of gesture or some other expression where the upper body half takes a major role.
A still further object of the present invention is to provide an ambulation control apparatus and an ambulation control method for effectively controlling an erect bipedal ambulatory robot so as to make it determine its gait of the lower limbs in response to that of the upper limbs (the term xe2x80x9cgaitxe2x80x9d as used herein is a technical term of the industry referring to xe2x80x9ctime series changes of the angles of jointsxe2x80x9d and having a meaning substantially same as xe2x80x9cpattern of movementxe2x80x9d).
According to the invention, the above objects are achieved by providing an ambulation control apparatus or an ambulation control method for controlling a robot of the type having at least lower limbs, a trunk and loins and adapted to bipedalism, said apparatus or method being adapted to obtain the pattern of movement of the entire body for walking by deriving the pattern of movement of the loins from an arbitrarily selected pattern of movement of the feet, the trajectory of the ZMP, the pattern of movement of the trunk and that of the upper limbs.
In a second aspect of the invention, there is also provided an ambulation control apparatus or an ambulation control method for controlling a robot of the type having at least lower limbs, a trunk and loins so as to make it move on its two feet of the lower limbs in order to cause the ZMP to get to a target position, said apparatus or method comprising:
(a) a means for or a step of selecting the motion of the feet, that of the trunk and that of the upper limbs and the attitude and height of the loins in order to realize a requested action;
(b) a means for or a step of selecting the trajectory of the ZMP on the basis of the motion of the feet selected by said means or in said step (a);
(c) a means for or a step of obtaining a solution for the motion of the loins for balancing the moment on the ZMP selected by said means or in said step (b); and
(d) a means for or a step of realizing the motion of the loins on the basis of the obtained solution for the motion of the loins.
In a third aspect of the invention, there is also provided an ambulation control apparatus or an ambulation control method for controlling a robot of the type having at least lower limbs, a trunk and loins so as to make it move on its two feet of the lower limbs in order to cause the ZMP to get to a target position, said apparatus or method comprising:
(A) a means for or a step of selecting the motion of the feet, that of the trunk and that of the upper limbs and the attitude and height of the loins in order to realize a requested action;
(B) a means for or a step of selecting the trajectory of the ZMP on the basis of the motion of the feet selected by said means or in said step (A);
(C) a means for or a step of obtaining an approximate solution for the motion of the loins for balancing the moment on the ZMP selected by said means or in said step (B) by means of a non-strict model;
(D) a means for or a step of obtaining an approximate solution for the motion of the loins for balancing the moment on the ZMP selected by said means or in said step (B) by means of a non-strict model;
(E) a means for or a step of finalizing the solution for the motion of the loins when the difference between the approximate solution obtained by said means or in said step (C) and the approximate solution obtained by said means or in said step (D) is less than a predetermined admissible value;
(F) a means for or a step of modifying the moment on the ZMP of the non-strict model and inputting the modified value to said means or step (C) when the difference between the approximate solution obtained by said means or in said step (C) and the approximate solution obtained by said means or in said step (D) is not less than the predetermined admissible value; and
(G) a means for or a step of realizing the motion of the loins on the basis of the obtained solution for the motion of the loins.
For the purpose of the invention, the non-strict model in an ambulation control apparatus or an ambulation control method according to the third aspect of the invention may be a linear and/or non-interference multiple material point approximation model for robots. On the other hand, the strict model in an ambulation control apparatus or an ambulation control method according to the third aspect of the invention may be a rigid body model or a non-linear and/or interference approximation model of a multiple material point system.
An ambulation control apparatus or an ambulation control method according to the third aspect of the invention may further comprises (Cxe2x80x2) a means for or a step of reselecting/modifying the pattern of movement of the trunk and that of the upper limbs when the selected motion of the trunk and that of the upper limbs cannot be realized by the approximate solution obtained by said means for or in said step of, whichever appropriate, obtaining an approximate solution for the motion of the loins by means of a non-strict model (C).
For the purpose of the invention, said means for or said step of obtaining an approximate solution for the motion of the loins by means of a non-strict model (C) of an ambulation control apparatus or an ambulation control method according to the third aspect of the invention may be a means for or a step of, whichever appropriate, obtaining an approximate solution for the motion of the loins by solving a balancing equation of the moment on the selected ZMP generated by the motions of the feet, the trunk and the upper limbs and the moment on the selected ZMP generated by the horizontal plane motion of the loins.
Alternatively, said means for or said step of obtaining an approximate solution for the motion of the loins by means of a non-strict model (C) may be a means for or a step of, whichever appropriate, replacing the time function with a frequency function for computation.
Still alternatively, said means for or said step of obtaining an approximate solution for the motion of the loins by means of a non-strict model (C) may be a means for or a step of, whichever appropriate, computationally determining the Fourier coefficients of the horizontal plane trajectory of the loins by applying a Fourier series development to the moment on the selected ZMP generated by the motions of the feet, the trunk and the upper limbs and also to the horizontal plane trajectory of the loins and additionally obtaining an approximate solution of the motion of the loins by applying an inverse Fourier series development.
In a fourth aspect of the invention, there is also provided an ambulation control apparatus or an ambulation control method for controlling a robot of the type having an upper body half provided with a plurality of joints for expressing an action of the upper body half and a lower body half having leg joints at least for realizing an ambulatory action, the gait of the lower body half adapted to stable walk being determined according to the gait of the upper body half.
Thus, an ambulation control apparatus or an ambulation control method according to the invention can realize the motion of the loins of a robot adapted to stable walk on the basis of a selected pattern of movement of the trunk and that of the upper limbs in addition to that of the feet. The motion of the trunk and that of the upper limbs correspond to the gait of the upper body half that is an action of expression including gestures that uses the upper body half.
Therefore, according to the invention, a robot can determine the gait of the lower limbs so as to realize a stable walk regardless if the robot is standing upright or walking. Particularly, if the robot is made to gesture, using the upper body half including the upper limbs and the trunk while standing upright, it can determine the gait of the lower limbs so as to make a stable walk in response to such a gait of the upper body half.
According to the invention, there is provided an ambulation control apparatus and an ambulation control method for effectively controlling a robot having a structure that is adapted to mimic the mechanism and the behaviour of a living body.
Additionally, according to the present invention, there is also provided an ambulation control apparatus and an ambulation control method for effectively controlling a bipedal ambulatory robot having a structure that is adapted to mimic the mechanism and the behaviour of an erect biped such as man or ape.
Still additionally, according to the present invention, there is also provided an ambulation control apparatus and an ambulation control method for effectively controlling an erect bipedal ambulatory robot having lower limbs adapted to erect bipedalism and amounted with an upper body half including a torso, a head and arms.
Still additionally, according to the present invention, there is also provided an ambulation control apparatus and an ambulation control method for effectively controlling a robot so as to make it walk stably and keep on behaving like a man and being rich in expressions.
Still additionally, according to the present invention, there is also provided an ambulation control apparatus and an ambulation control method for effectively controlling an erect bipedal ambulatory robot having lower limbs adapted to erect bipedalism and amounted with an upper body half including a torso, a head and arms so as to make it recover the stability of attitude whenever the latter is lost due to an action of gesture or some other expression where the upper half of the body takes a major role.
Furthermore, according to the present invention, it is now possible to provide a robot adapted to erect bipedalism and designed to generate a pattern of movement of the loins to generate a corresponding pattern of stable motion of the lower half of the body which may be from-the-trunk-down (or from-the-loins-down). Therefore, if the attitudinal stability of the robot is lost due to an expression such as gesture led by the upper body half, it can be recovered by an appropriate motion of the lower half of the body.
In the case of a bipedal ambulatory robot having six degrees of freedom at each lower limb, the attitude of each leg is unequivocally determined by the position of the corresponding foot and the height of the corresponding loin. In other words, the generation of a pattern of movement of the loin means that the attitude of the leg and hence the gait of the lower limb is determined by it. Thus, with an ambulation control apparatus or an ambulation control method according to the invention, it is possible to determine the gait of the lower body half that is adapted to stable bipedalism in response to the gait of the upper body half.